1. Technical Field
This invention relates in general to integrated microelectronic devices having a field emission cathode structure and, more particularly, to novel lateral field emission device structures and methods of fabricating the same.
2. Description of the Prior Art
Field emission devices (FEDs) or micro-vacuum tubes have many advantages over conventional semiconductor silicon devices for signal and data processing. For example, FEDs are much faster switching in the terahertz regime, are temperature and radiation insensitive, and are relatively easy to construct. Applications range from discrete active devices to high density SRAMs and displays, radiation-hardened military applications and temperature insensitive space technologies, etc. The literature on field emission devices principally focuses on process problems associated with producing the sharpest tip (e.g., with photolithography), controlling cathode to anode and cathode to gate distances and achieving self-alignment between these elements. By way of example, reference is made to U.S. Pat. No. 4,990,766, entitled "Solid State Electron Amplifier," and U.S. Pat. No. 4,721,885, entitled "Very High Speed Integrated Microelectronic Tubes." In these devices, as in all known field emission devices, the sharply pointed tip of the cathode is the only physical structure that is not commonly produced by standard integrated circuit fabrication processes.
Activity in the field of cold cathode emission at VLSI levels has been increasing in the past few years. The present application is believed to further advance the state of this art by providing FEDs which have cathode tips produced by integrated circuit fabrication processes. Further, FED structures are provided with extremely fine cathode tips, exact control of cathode to anode distance and exact alignment of gate and cathode, along with precise distance control of gate to cathode. In addition, the cross-sectional area overlap of gate to cathode is kept low to minimize coupling capacitances. In another aspect, presently available field emission devices are often characterized by low active current. The typical solution to this problem has been to couple multiple structures in parallel, which works but is expensive in terms of the layout area required. The structures and methods of fabrication described below provide significant advantages in device current and circuit layout area.